Monday, 22 June 2020

Heat Related Problems in Children

As a heatwave hits the UK, we can expect a significant number of children to present with heat related problems.  In the vast majority of cases, these will be benign and self-limiting.  In a small proportion, heat can cause serious illness.

The effects of excessive environmental heat in children are well described but there is a lack of a decent evidence base regarding incidence and effectiveness of treatment.  It is often stated that children are more at risk due to their increased body surface area to weight ratio, however true heat related illness is rare in children and admission to hospital is even less common.  It is likely that there are several protective factors including their robust physiological compensatory mechanisms and human factors which help to keep them from becoming seriously unwell.

Common heat related presentations in children

Heat rash (Miliaria)

Also called prickly heat or sweat rash, a raised erythematous itchy rash is a common problem during a heatwave.  The pathogenesis is to do with increased sweat gland secretion and the inflammatory effects of this.  Miliaria is not harmful but it is uncomfortable.

The child with miliaria will be well and there are no systemic effects.

Prevention and non-pharmacological treatment are one and the same for miliaria.  Avoiding prolonged exposure to excess heat is the single most important intervention.  Parents should enable the child to rest in a cool environment out of the sun.  Unsurprisingly hydration is also important.

Pharmacological interventions include calamine lotion and antihistamines.

Swollen hands and feet (Heat oedema)

Heat oedema is less common than heat rash but also seen in significant numbers of children during a heatwave.  The mechanism for this occurring is the physiological peripheral dilation of the peripheries.  As with miliaria, there will be no systemic effects on the child, who should be otherwise and obviously well.

Non-pharmacological treatments are also the mainstay of treatment of heat oedema.  Diuretics should never be used due to the risk of precipitation dehydration or electrolyte imbalance.  Cooling down, resting and drinking are what these children need.


This is not really a heat related problem but is seen much more commonly during a heatwave.  When the sun is out, children often play outdoors with more skin exposed.  Certain plants leave chemicals on the skin which are activated by sunlight.  This then leads to dermatitis.

Children with phytodematitis will be well but have an itchy papular rash in areas of exposed skin, sparing the area that was clothed at time of exposure.  The rash is usually self-limiting but in some cases can go on to cause hyperpigmentation.  Acutely treatment is symptomatic with antihistamines and a short course of topical steroids as pharmacological options.


Again, sunburn is not caused by heat but by exposure to sunlight.  Significant sunburn can be a contributing factor to dehydration.  It should therefore be included in the assessment of risk when a child presents with more significant heat related symptoms.


Children and young people are well known to have a high incidence of vasovagal syncope.  The reason for this peak, often seen in adolescents is not fully understood.  Heat related syncope is also a reasonably common presentation in children and young people.  As with vasovagal syncope, the assessment of heat related syncope in children is all about establishing a typical history and excluding red flags.

The child with heat syncope who has made a good recovery should be managed with preventative measures to avoid a further episode - rest, a cool environment and good hydration.  Note that there is no specific evidence to recommend any specific hydration fluid over another for these minor heat related illnesses.  Water is probably as good a place to start as any.

Uncommon heat related presentations in children

Heat related illness that makes a child systemically unwell is relatively uncommon.  When it does occur, there are usually risk factors or extreme and prolonged exposure to excessive heat.  Paediatric patients most at risk of significant heat related illness are those who cannot regulate their own fluid intake or clothing/ environment such as babies and children with neurodisability that impairs the ability to self-care.

The greatest risk usually comes from the combination of risk factor and environment, such as a baby left in a car on a hot day.

Another risk factor is the extremem change in environmental temperature.  Humans have an ability to adapt to different environments, a process that occurs over the space of weeks.  This allows us to cope with the change in seasons.  When weather goes from a relatively cool period to very hot weather suddenly (i.e. a heat wave), that adaptation can't happen, thus the sudden rise in heat related illnesses disproportionate to the actual outside temperature.

Significant heat related illness is different from the above conditions because there are systemic manifestations of a combination of over-heating and dehydration.  The range of presentations is a spectrum of illnesses which include heat stress, heat exhaustion and heat stroke.

Heat stress

Heat stress is the mildest form of heat related illness with systemic effect.  With heat stress, the child is feeling the effects of heat and they will let you know about it in an age appropriate way.  Children with heat stress may be tired, grumpy, and have headache or general aches and pains.  Babies will cry excessively or be fussy with feeds.

A key feature of heat stress is that body temperature is not raised and there is normal function.  Heart rate is normal if the child is settled.

Heat stress should be managed with paracetamol (acetaminophen) for the pain*, rest, oral fluids and a cool environment.  This can be done in a pre-hospital setting with safety-netting advice.

*Paracetamol does not reduce body heat when it is due to environment and dehydration.

Heat exhaustion

Heat exhaustion is a more extreme systemic effect from the same combination of excessive heat and poor hydration.  Children with heat exhaustion will be more unwell and are on a downward spiral as they may start to vomit or have diarrhoea.  They will be more affected by how unwell they feel, but their conscious level should be normal.

The child with heat exhaustion is likely to have a raised body temperature somewhere above 38°C but below 40°C.  Dehydration and the heat effect will manifest as tachycardia and the child will look more unwell.  End organ function is still normal at this stage, but the child is at risk of deterioration due to the cycle of symptoms impairing hydration.

The management of heat exhaustion is similar to heat stress but with the addition of active cooling.  The most commonly recommended method for this is to place the child in a cool bath.  The temperature of water for this intervention is ill-defined but it should feel cool and not be cold enough to make the child shiver.  An alternative way of cooling is the use of cool wet towels.

Children with heat exhaustion may be managed in an Emergency Department or Paediatric acute ward and discharged when they are normalising.  Oral hydration is normally achievable.  If vomiting is an issue, anti-emetics or nasogastric fluids are options.

Heat Stroke

Heat Stroke is rare in children.  It is the seriously ill end of the spectrum of heat related illness.  Like sepsis, it has a definition that doesn't work well in the initial assessment of the child.  For the front line clinician, the bottom line is that the child who looks seriously unwell due to heat exposure should be presumed to have heat stroke.

One of the most consistent features is the central nervous system effects of heat stroke.  Children become severely confused or agitated to begin with and then progress to coma.  Seizures are a common problem in heat stroke and risk further increasing body temperature.

As with all heat related illness, simple measures are still important.  The child should have clothing removed and placed in a cool environment as soon as possible.  Applying cool wet towels can be used to begin the cooling process.  Once in a hospital setting the child will need critical care level management.  Airway management, venous access and intravenous fluids (room temperature normal saline) are all key interventions while getting expert help.  For the hospital physician wanting more information about the ongoing management of heat stroke in children, I would recommend this article.
So, while rashes, swollen peripheries and simple faints are the things that you are most likely to see, there is always the risk that the overheated child is on the slippery slope of heat related illness.  Children who are alert and able to drink can be managed with good advice and safety-netting.  Stay cool, rest up, drink plenty and come back if you're getting worse.

Enjoy the sunshine but stay safe.  If the UK weather does what it normally does, next week's topic will be the management of the hypothermic child.

Edward Snelson